The present invention relates to a new and improved construction of pendulum shear for a continuous casting installation wherein the shear is provided with a mechanical drive for the pulse-like cutting operation, there is further provided a knife or cutter which is rigidly connected with the pendulum and movable by means of a driven crank towards a second cutter, and furthermore, there is provided mechanism for the acceleration of the pendulum out of its rest position at approximately the maximum opening of the knife in the direction of travel of the strand, this mechanism prior to the cutting operation accelerating the pendulum in its cutting range or region to a speed approximately corresponding to the speed of movement of the strand.
For the cutting of strands, especially billets of steel, which depart from the withdrawal device of continuous casting installations there are known to the art mechanical pendulum or flying shears. Such pendulum shears are equipped with a mechanical drive which can be connected and disconnected with the crank shaft of the pendulum for the pulse-like cutting operation. A knife or cutter rigidly connected with the pendulum is moved by the crank towards a second knife or cutter. The major portion of the displacement path of the closing movement of the knife can be used with such shears for cutting. The pendulum, upon receiving the cutting pulse or command from the strand length measuring device, is located in its rest position at the region of the dead-center with approximately maximum knife opening. A mechanism for accelerating the pendulum out of its rest position prior to the cutting operation in the direction of movement of the strand to a speed which approximately corresponds to the speed of movement of the strand, consists of a hydraulic piston-cylinder unit which is hingedly connected at the pendulum and at the stand or housing. Such hydraulic drive for the pendulum acceleration and for pendulum movement during and after the cutting operation as well as for the return of the pendulum back into the rest position, however, requires an extensive and expensive control. Additional, such controls owing to the short time cycles for such course of movement, on the one hand, and because of a certain inertia of the hydraulic system on the other hand, are only adjustable with corresponding expenditure in such a manner that during coupling the knife at the strand and during the cutting operation there do not occur any disadvantageous appreciable decelerations in the mould or accelerations of the strand movement. Particularly in the case of small billet shapes and high casting speeds decelerations or retardations can lead to overflowing of the mould and accelerations can lead to breakouts. Moreover, due to such sudden changes in speed of the strand within the mould there can occur surface defects. If for, quality-, format- or other reasons the casting speed must be changed frequently, then such shears additionally require expensive pre-programmed controls.